Abstract/Project Summary Neurologic disability due to hypoxic-ischemic injury is the leading cause of long term morbidity in children with congenital heart disease (CHD). Many deficits cannot be reliably detected until years after surgery, making neurologic outcomes difficult to predict and creating a critical need for an early biomarker. The long term goal of this application is to improve the diagnosis and management of brain injury in CHD by identifying serum bi- omarkers for neurodevelopmental outcomes that can facilitate clinical trials of neuroprotective strategies and help guide treatment. The specific objective is to use novel high-throughput transcriptomic and proteomic tech- nologies, ex vivo and in vivo neuroimaging and innovative computational methods to characterize tau in normal human brain development and following hypoxic-ischemic injury due to CHD. Our hypothesis is that tau ex- pression, splicing and phosphorylation change during development and in response to hypoxic-ischemic injury, leading to changes that can be detected in serum and used as biomarkers of neonatal hypoxic-ischemic injury. Our rationale is that understanding these changes will permit the use of tau as a serum biomarker of neonatal brain injury, thus improving outcomes for these patients. We plan to test our hypothesis by: (1) Characterizing tau splicing in human brain development and CHD using hybrid RNA sequencing (RNASeq/IsoSeq) and RNA using in situ hybridization (BaseScope), (2) Characterizing tau post-translational modification in the same set- tings multiplex serial immunofluorescence (Opal), immunohistochemistry and immunoblotting and (3) validating tau as a serum biomarker of hypoxic-ischemic brain injury using single molecule array (Simoa) ELISA in a dis- covery cohort of infants with CHD. The research proposed in this application is innovative because it applies novel methods, including long-read RNA sequencing, BaseScope, high-resolution ex-vivo MRI and Simoa, to a heretofore under-studied role of tau in human development and as a potential candidate biomarker in CHD. The proposed research is significant because it is the first step towards the development of clinically useful bi- omarkers for neurologic outcomes in congenital heart disease and neonatal hypoxic-ischemic injury in general, thus facilitating clinical trials and improving outcomes in these patients. At the same time, the proposed project is designed to provide critical career development training to the candidate. The proposal builds upon the can- didate's established interest in developmental neuropathology and his prior training in computational genetics and translational research. The candidate?s primary mentor, Dr. Alex Bassuk, is an experienced clinician and developmental neuroscientist and will be supplemented by co-mentors with specific expertise in translational neuroscience (Dr. Abel), tau biology (Dr. Crary) and neuroradiology (Dr. Panigrahy). They will assure that the proposed research and training prepare the applicant to be an independent investigator in developmental neu- ropathology with a strong background in modern molecular techniques.